1. Field of the Invention
The present invention relates to a power source plug inserted into a power outlet of a commercial power source, for example, a power source receptacle for supplying electric power to an electrical equipment, or more particularly a power source plug with a gap filling material formed therein for preventing a tracking fire (a fire caused by the short-circuiting or shorting due to the dust, dirt or the like deposited).
2. Description of the Related Art
Electrical equipment such as an electric appliance, an office automation equipment and so on each include a power source plug to be inserted into a power source receptacle for electrical connection. The connection terminal member of the power source plugs is slightly smaller in outer diameter than the inner diameter of a power source plug connection hole in order to permit insertion thereof into the power source plug connection hole of the power source receptacle. Consequently, when the power source plug is inserted into the power source receptacle, dust, dirt or the like attaches to the gap between the connection terminal member of the power source plug and the power source plug connection hole of the power source receptacle, thereby often causing a short-circuiting or other inconveniences.
When the power source plug is inserted into a power source receptacle, there is caused a gap formed between the connection terminal member and the power source, plug connection hole and hence is liable to become loose. The power source plug then easily tilts with respect to the power source receptacle and tends to come off easily from the power source plug connection hole. The power source plug thus would easily come off, if a leg is erroneously caught in a power source cord of the power source plug, for example. Especially with the office automation equipment or the like requiring incessant power supply, power would be interrupted by the coming-off of the power source plug, leading to the problem of the loss of the internal data thereof.
With the object of solving this problem, the specification entitled "Power source plug" disclosed in Japanese patent application No. 7-37388 filed earlier by the present applicant will be briefly explained as first and second prior applications with reference to FIGS. 1 and 2 showing the same.
A first prior art power source plug 1 comprises, as shown in FIG. 1, a plug body 3, a pair of connection terminal members 4A, 4B adapted to be inserted into power source plug connection holes 9A, 9B of a power source receptacle 2, and a power source cord 5 connected to an electrical equipment.
The plug body 3 has a profile thereof formed substantially rectangular and made of an insulating material having the insulating property like plastics or synthetic rubber or the like. Also, the plug body 3 is formed with a pair of gap filing members 6A, 6B integrally formed therewith upon its molding so as to be protruded from a butting surface 3A of the plug body 3 on which surface 3A the connection terminal members 4A, 4B are respectively inserted into power source plug insertion holes 9A and 9B of the power source receptacle 2.
These gap filling members 6A, 6B are formed in a rectangular cylinder having substantially the same outer diameter is the inner diameter of the power source plug connection holes 9A, 9B of the power source receptacle 2.
The gap filling members 6A, 6B, as shown in FIG. 2, include a pair of connection terminal insertion holes 7A, 7B each having an inner diameter substantially equal to the outer diameter of each of the connection terminal members 4A, 4B. Also, the gap filling members 6A, 6B are formed with chamfered portions 8A, 8B, respectively, at the tip ends thereof.
The connection terminal members 4A, 4B are made of a metal plate and, have the base end side thereof supported in the plug body 3, and the forward end portions thereof to be inserted into the power source plug connection holes 9A, 9B of the power source receptacle 2 are mounted on the plug body 3 so as to protrude from the connection terminal insertion holes 7A, 7B of the plug body 3. As a result, the outer peripheral walls of the roots of the connection terminal members 4A, 4B protruded from the plug body 3 are covered by the inner peripheral walls of the gap filling members 6A, 6B of the plug body 3, respectively.
With the first prior art power source plug 1 having the above-mentioned configuration, the connection terminal members 4A, 4B thereof are inserted into the power source plug connection holes 9A, 9B of the power source receptacle 2, respectively. Upon the insertion, the gap filling members 6A, 6B are filled the gaps 10A, 10B formed between the outer peripheral walls of the connection terminal members 4A, 4B of the power source plug 1 and the inner peripheral walls of the power source plug connection holes 9A, 9B of the power source receptacle 2. As a result, the gaps 10A, 10B disappear and hence dust, dirt or the like can not invade thereinto while at the same time preventing the loosening of the power source plug.
With the second prior art power source plug (not shown), on the other hand, gap filling caps (blade caps) are arranged separately from the plug body and therefore are detachable. By inserting the blade caps, the gaps are protected from intrusion of dust, dirt or the like.
In the above-mentioned first prior art power source plug 1, however, the gap filling members 6A, 6B are formed of the same material as and integrally with the plug body 3. Therefore, in the case where the plug body is made of a soft material such as vinyl chloride or the like, for example, the thickness of the gap filling members 6A, 6B is thin, thereby leading to the problem of a lower durability of the gap filling members 6A, 6B when they are inserted into the connection hales 9A, 9B of the power source receptacle 2.
With the second prior art power source plug, on the other hand, the blade caps are arranged so as to be detachable from the plug body formed separately. However, since the conventional blade caps have no means for connection with the plug body the inserted blade caps come off from the root of the plug body so that the connection terminal members 4A, 4B are exposed and thereby posing the threat of the intrusion of dust, dirt or the like in the gaps, in the case where a force is applied to depress the plug body down or in the case where the plug body is in a state liable to come off.